Reciprocity is a Black Ladies Chatham Studs Sandal Viking 0817tqgw that involves in-kind exchanges between people—responding to another’s action with another equivalent action. It is usually positive (e.g. returning a favor), but it can also be negative (e.g. punishing a negative action) (Fehr & Gächter, 2000). Reciprocity is an interesting concept from the perspective of BE, because it does not involve an economic exchange, and it has been studied by means of experimental games (see game theory). Charities often take advantage of reciprocity when including small gifts in solicitation letters, while supermarkets try to get people to buy by offering free samples. Reciprocity is also used as a social influence tool in the form of ‘reciprocal concessions’, an approach also known as the ‘door-in-the-face’ technique, which occurs when a person makes an initial large request (e.g. to buy an expensive product), followed up by a smaller request (e.g. a less expensive option), if the initial request is denied by the responder. The responder then feels obligated to ‘return the favor’ by agreeing to the conceded request (Cialdini, Vincent, Lewis, Catalan, Wheeler, & Darby, 1975).